oil cooler kz 750 twin m1?

Does anyone know if I can install a external oil cooler on my engine, know the larger displacement engines you can?

Charles, you question is hard to decipher. First, I am not sure what the oil sending pipe looks like on your bike but if it is the same as on a 900/1000, then you can certainly install an oil cooler. If it isn't the same, someone in the aftermarket must have had to manufacture a replacement oil sending pipe. This is the deal behind the cylinder that has the wire that picks up oil pressure connected. I am sure there are 750 owners who know the answer for sure. I don't understand the question regarding displacement.

I have done some research on the subject, and the only way that I have found to install an oil cooler on a 750 twin is to hook a line to the present oil pressure sender location, and drill a hole into the crankcase to return the oil back into the sump. This means the oil cooler is a bypass cooler, this means the oil goes from the oil pump, through the filter, into the main oil gallery, out through the former location of the oil pressure sender, through the oil cooler, then back into the sump, bypassing the rest of the motor and all the bearings, etc. I don't think the 750 twin oil pump has sufficient capacity to bypass the oil though an oil cooler and still provide the required volume and pressure to the main, rod, and cam bearings.

If you do install an oil cooler, then I strongly suggest that you install an oil pressure gauge so that you can monitor the oil pressure.

Post edited by: steell, at: 2006/02/06 10:04

Steve, I take it the 750 twin has no oil pipe deal behind the block where a pressure sending unit is installed? In any case, as far as pressure to push oil through a cooler, the 650, 900 and 1000 are also low pressure systems and they seem to do OK. Does the 750 have a less powerful pump than a four cylinder?

The 900/1000 are low pressure systems because they use roller bearings for the mains and rods, the 650 and 750 fours and twins have a higher oil pressure because they have plain beaing cranks and rods.
The 750 fours with factory oil coolers have a full flow oil cooler, the oil goes through the cooler then to the rest of the motor.
I don't know how people install an oil cooler on anything other than the 750 twins, because that's the only thing that I have been interested in installing a non stock oil cooler on. My GPz750 motors are factory equipped with oil coolers.

Smithgpz and I had this discuusion on the old board (it's in the archives), and both of us concluded it would not be a wise idea after studying the oil flow path in the factory manual.

Yes the 750 twin has an oil pressure switch behind the cylinders where you could install a line to the oil cooler, but the problem is there is no place to return the oil other than the sump (bypassing the motor). The 650 and 750 fours have a plug on the right side so you can return the oil to the main gallery, and I suspect that's what most people do.

In the future I may investigate the possibility of modifying the oil system in the twin so I can use a full flow oil cooler, but I'll wait and see if I am going to need it. Stock compression for the 750 twin is 8.5:1 and mine has 10:1 and should have 50% more power than stock (for other reasons in addition to compression).

I just took a look at the 650 and 750 twin manuals, and the oil pressure relief valve opens at 63 psi on the 650 and 48 psi on the 750 twin. I don't have a 1000 manual handy, but I think the oil pressure runs around 15-20 psi, it's hard to run much pressure with roller bearings.

Post edited by: steell, at: 2006/02/06 14:08

So I take that i am unable to install an oil cooler, I have the factory service manual and there is no return line without dilling into the engine case. This bike has only 7,846 miles on it, and I live in memphis it gets over 90 degree's in the summer. I will be using this bike for my dialy commute 60 miles round trip interstate travel and lots of stop and go when I get into the city. thanks for he help guys

Charles, I suspect you will have no problems operating the twin up in steamy Tennessee in the summer. I would be more concerned about oil in the winter with an oil cooler on. I have an oil temp gauge on one of my KZs and it always distressed me that when outside temps were in the 40s, the bike's oil didn't warm significantly for almost 20 miles... I didn't have a bypass on my oil cooler which I have since removed.

CHARLESRAD wrote:

...This bike has only 7,846 miles on it, and I live in memphis it gets over 90 degree's in the summer. I will be using this bike for my dialy commute 60 miles round trip interstate travel and lots of stop and go when I get into the city...

I do about the same commute on my 750, with the same temps here in suburban Detroit. Oh, and the humidity! :sick:

Anyway, my bike gets pretty warm, but I have found that a nice low idle and a cool plug (B8ES) and I'm good to go. Stoplights *are* brutal at 90+ degrees, but the bike cools down quickly with any movement...